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目的探讨年龄因素对大鼠海马齿状回神经发生的影响及新生神经细胞的分化。方法选择7、14、28、60、180 d 5个日龄组SD大鼠,每组8只,雌雄不限。采用5-溴脱氧尿核苷(BrdU)标记新生细胞,以β微管蛋白(TuJ1)、胶质纤维酸性蛋白(GFAP)双标免疫组织化学方法分别标记其神经元和胶质细胞,检测不同日龄大鼠海马齿状回神经发生,了解新生细胞向神经元细胞和神经胶质细胞分化比例。结果5个日龄组大鼠均有海马齿状回颗粒细胞层神经发生现象,细胞形态多样,呈圆形、椭圆形、菱形等,胞核较大,分布于整个颗粒细胞层。日龄7、14、28、60、180 d组大鼠BrdU阳性细胞数分别为158.07±5.37、141.28±7.27、116.93±9.24、76.56±6.88、41.42±4.45,随着日龄的增长,大鼠海马齿状回新生细胞数量渐减少(P<0.05);日龄7、14、28、60、180 d组大鼠BrdU阳性细胞同时表达TuJ1的比例分别为81.6.%、78.9%、83.9%、80.2%、82.4%,组间比较无明显差异(P>0.05);各组新生细胞中4%～5%为GFAP阳性。还有少数齿状回的BrdU阳性细胞并不同时表达TuJ1或GFAP。结论在生理状态下不同日龄大鼠海马齿状回存在神经细胞增殖现象,而且随着日龄增加,神经元再生的能力渐减弱,新生细胞多分化为神经元细胞。
Objective To investigate the effect of age on the neurogenesis of the dentate gyrus in hippocampus and the differentiation of newborn neurons. Methods Sprague-Dawley rats of 5-day-old group were selected on the 7th, 14th, 28th, 60th, and 180th days for 8 days. BrdU-labeled neonatal cells were used to label their neurons and glial cells with the double-labeled immunohistochemical method of Tu-1 and GFAP. Day-old rat hippocampal dentate gyrus, to understand the newborn cells to neuronal cells and glial cell differentiation ratio. Results All 5-day-old rats had neurogenesis in the granular layer of dentate gyrus in hippocampus. The cells in the 5-day-old group had various morphological changes, such as round, oval and rhombus with large nuclei distributed throughout the granulosa cell layer. The number of BrdU positive cells in the 7, 14, 28, 60 and 180 d groups were 158.07 ± 5.37, 141.28 ± 7.27, 116.93 ± 9.24, 76.56 ± 6.88 and 41.42 ± 4.45, respectively. With the increasing of age, The numbers of dendritic cells in the hippocampus gradually decreased (P <0.05). The percentage of TuJ1 cells expressing BrdU positive cells in the 7, 14, 28, 60 and 180 d groups were 81.6%, 78.9% and 83.9% 80.2% and 82.4%, respectively. There was no significant difference between the two groups (P> 0.05). In all groups, 4% ~ 5% of newborn cells were positive for GFAP. There are also a small number of dentate gyrus BrdU positive cells do not express TuJ1 or GFAP at the same time. Conclusions The proliferation of neurons in hippocampus of rats of different ages at physiological status is regressed. With the increase of the age, the ability of neurons to regenerate gradually diminishes and the newborn cells differentiate into neurons.